Means and method for stacking sheets of paperboard or cardboard



Jan. 10, 1967 J. E. KNECHT 3,297,318 MEANS AND METHOD FOR STACKING SHEETS OF' PAPERBOARD OR CARDBOARD Filed March 26, 1964 4 Sheets-Sheet l INVENTOR JOHN E. KNECHT ATTORNEYS Jan. 10, 1967 J. E. KNEcH-r 3,297,318

MEANS AND METHOD FOR STACKING SHEETS OF PAPERBOARD OR CARDBOARD Filed March 26, 1964 4 Sheets-Sheet 2 INVENTOR JOHN E. KN ECHT ATTORNEYS Jan. 10, 1967 J. E. KNECHT 3,297,318

MEANS AND METHOD FOR STACKING SHEETS OF PAPERBOARD OR CARDBOARD INVENTOR JOHN E. KNECHT ATTORNEYS Jan. 10, 1967 J. E. KNECHT 3,297,318

MEANS AND METHOD FOR STACKING SHEETS OF PAPERBOARD OR CARDBOARD Filed March 26, 1964 4 Sheets-Sheet 4 |30 |32 FIG. 5 '78 llNvr-:NTOR FIG. 6 JOHN E. KNECHT ATTORNEYS United States Patent Oice 3,297,318 Patented Jan. 10, 1967 3,297,318 IVIEANS AND NIETHQD FOR STACKING SI-EE'IS OF PAPERBOARD OR CARDBOARD John E. Knecht, Pointe Claire, Quebec, Canada, assignor to Bathurst Paper Limited Filed Mar. 26, 1964, Ser. No. 354,959 13 Claims. (Cl. 271-68) This invention relates to means and a method for stacking sheets of paperboard or cardboard, and processing such sheets after they are stacked.

Where sheets are referred to herein, it is assumed that such sheets are at, usually although not necessarily, rectangular and made of cardboard or paperboard.

This invention deals with the stacking of sheets being continually supplied to the stacking location. Machines are well known which will stack sheets travelling on a conveyor and delivered to the stacking location. However, machines of this type presently in use are not adapted to allow the removal of a pile of stacked sheets without interruption of the stacking operation. Machines have been proposed which interposed a part of the machine which formed a shelf between sheets in a stack, at a predetermined height, whereby to support the stack thereabove, while stacked sheets below said shelf are removed. However, such latter machines have shown a tendency to jam sheets during the interposition procedure or conversely the sheets have jammed the interposition mechanism.

It is therefore an object of this invention to provide means and a method for clamping a sheet or sheets located a predetermined distance above the base of a continually rising stack by pressure applied on opposed sheet edges. The sheet or sheets so clamped therefore act as a shelf for the sheets being added at the top of the stack, while the stacks of sheets below those clamped may be removed. Means are provided allowing return of the clamped sheets to the height of the original stack base, to form the base of a new stack, whereby the procedure may be cyclically repeated and the above operations are performed without interruption of the addition of the sheets to the top of the stack.

In the drawings:

FIGURE 1 shows a perspective view of the device, and

FIGURES 2, 3, 4, 5 and 6 indicate operation of the device.

In the drawings, the sheet stacking operation is performed on a stacking surface wherefrom the stacks of sheets may be removed during the operation of the device. In the preferred embodiment, this surface takes the form of parallel rollers mounted on opposed members 12 to fbrm, collectively, a base for a rising stack of sheets and a path for removal of a stack of sheets. The upper flight of a belt 14 overlies the rollers and forms a frictional base for sheets stacked thereon and, driven by motor 16, provides the means to move a stack along the conveyor when required. The motor 16 is normally off and is turned on and off by means to be discussed hereafter.

The direction of movement of the upper flight of belt 14 defines an up-conveyor and down-conveyor direction, and at the up-conveyor end a pair of standards 18 extends upwardly from the base on opposite sides of the conveyor. A frame 20, of generally rectangular shape in plan view, is mounted to be vertically movable on the standards. This may be done in any desired manner, but in the preferred embodiment there are provided rollers 22 adapted to roll on the down-conveyor side of the standards and rollers 24 adapted to roll on the up-conveyor side. Such construction effectively rollably connects the frame to the standard.

The height of the frame 20 relative to the rollers 10 is controlled in any desired manner, such as yby a pair of chains 26 connected between sprockets 30 and the shaft of motor 28 at the bottom of the standards 18 and sprockets 31 rotatably mounted adjacent the top of standards 18. The operation of the motor 28 is controlled as hereinafter described.

The frame 20 provides a guide for a stack of sheets continually rising, by the successive addition of sheets to the top, with each sheet lying on and parallel to the one below. Such guide comprises, in the preferred form, a backstop 30 of generally vertical orientation and facing the upconveyor direction. The backstop 30 is mounted on a subframe 32, which is constructed to be slidable and therefore adjustable in the conveyor direction on the side members 34 of frame 20.

The backstop 30 extends vertically for the lower portion of its height, and the upper portion 36 is sloped upwardly and in the down-conveyor direction. Side walls 38 extend a short distance in the `rlp-conveyor direction from `adjacent each end of the backstop 30 and are spaced to provide side guides for the corresponding edges of the-sheet when such sheets are stacked adjacent thereto with one edge aligned with and adjacent to backstop 30. To assist in the guiding function, the side walls 38 are shaped to slope outwardly and upwardly adjacent the sloped portion 36 of the backstop 30 and to extend thence upwardly to ensure that sheets may be received between the side walls 38 and guided into the desired alignment by the sloping walls 36 and the vertical portion of backstop 30. The side walls 38 are mounted on the subframe 32 to be adjustably slidable, transversely, relative to the conveyor, to allow adjustment of the side walls to the desired sheet width.

Standards 40 extend upwardly from the frame 20, adjacent the main standards 18 but on the up-conveyor side thereof, with projections 41 extending in the down-conveyor direction between standards 18, and a Cross-member 42 is attached to projection 41 at the outer extremity thereof and projecting on each side of the standards 41. A roller 44, carrying one end of a conveyor belt for sheets, extends between the standards 40 and is rotatably mounted on blocks 46, which are slidably mounted on rods 43 which extend vertically between projections 41 and frame side members 34, and the opposed -blocks are jointed and rigidly connected by a crossbar 48.

Cylinders 50 are mounted on the projections of crossmember 42, and the corresponding piston rods 51 are connected to crossbar 48.

Such cylinders 50 form the height control for the roller 44, relative to the cross-member 42. The cylinder rods 51 controlled through hydraulic lines as shown will be described hereinafter.

Extendable members 56, defining a vertical guide surface 52 facing backstop 30, connect the crossbar 48 to a cross-member 54 mounted on the fra-me 20 adjacent the base of the rods 43. In the preferred embodiment .these extendable members 56 comprise relatively wide resilient rubber strips with their ilat sides facing the backstop, which strips stretch or contract to extend across the space between crossbar 4S and cross-member 54.

The bottom portion of the side of backstop 30 facing cross-member 54 is made of sponge rubber 57, and the entire surface of the backstop, including such sponge rubber, is covered with frictional material such as cotton belting 58.

Opposite the sponge rubber 57 rectangular areas of the cross-member 54 are cut away to allow the movement therethrough of clamping members to described.

A crossbar 60 is mounted on the frame 20 on the side of main standards 18 remote from backstop 30 to slide reciprocally in the travel position between a retracted and an extended position. Mounted on crosspiece `60, slidable in the conveyor direction relative to frame and oriented to face the backstop 3i), are a number of clamping plates 62 shaped to pass through the cut-away portions of cross-member 54, and mounted to move from a position on the side of cross-member 54 remote from the backstop 30, in the retracted position of the crossbar 60, and a position just slightly projecting from the cross-member 54 toward the backstop 36 in the extended position.

lPistons and piston cylinders 64 pneumatically actuable, in a manner to be described, mounted on the frame 20, are connected by their rods to move the clamping plates 62 and crossbar 60 between extended and retracted positions. Pneumatic lines to be described, are yprovided to control the movements of the pistons 64 and such lines are connected to a source and exhaust through a reversing valve controlled by a limit switch to be described.

Fingers 66 are pivotally mounted `by means of shaft 68 on crossbar 60, which ngers are connected to move from a retracted position clear of a stack guided by backstop 30 and surfaces 56 to an extended position adapted Ito bear upwards on and support sheets held by the clamping plate 62.

Fingers 66 are all keyed to or otherwise rotatable with a common shaft 68 for common rotary movement, and an arm 70 projects radially from the common shaft 68 land is connected to be rotated by a piston rod 72 slidable and movable by piston cylinder 74 which are swingiably mounted on the crossbar 60.

Pneumatic supply and return lines, interchangeable by a reverse valve, are connected to the cylinders 74 and are connected to actuate the cylinders 74 and piston rod 72 to operate the fingers either to a retracted or to an extended position, in a manner to be described.

Belt 76 is connected at one end to roller 44 and at the other end to a roller 78. The roller 78 is resiliently mounted on a base in any desired manner, such as the one shown, to be biased away from frame 20 but movable theretowards, against the bias, to conform with movements of roller 44.

A photocell 80 is mounted on frame 20 and located a predetermined but adjustable height above the side members 34 of frame 20, and a light source 81, similarly mounted, is placed across the frame from the cell to dene a light path therebetween. The location of source 81 and cell 80 is such that a stack of sheets will interrupt the photocell light path. The photocell 80 is connected to the control for motor 28 in such a way (to be described) that during the period of intermittent raising of frame 20 when the path from light source to photocell is interrupted, the motor 28 is switched on, and when the path is clear, the motor is switched ot. Thus, when moving under control of the photocell, the motor keeps the frame in position relative to the top of the stack.

Limit switch 82 is located on main standards 18 toward but below the top thereof, to be operated to actuate supply to cylinders 64 to cause the clamping plates 62 to be moved from retracted to extended position to bear on one edge of the sheets and to press the edge against the cotton belting 58 overlying sponge rubber backing.

Limit switch 87 is located below limit switch 82, at the desired height to decrease the relative height of rollers 44 to the top of the stack, during the upward travel of the frame 20 and to increase such relative height during the downward travel of frame 20,

Limit switch 84 is located above limit switch 82 and is connected to actuate cylinder 74 to rotate fingers 66 up under the lowermost clamped sheet for support thereof and also actuates the motor driving belt 14 to move conveyor and sheets stacked thereon clear of the conveyor. Limit switch 84 also acts, after a sutiicient time delay to allow the portion of the stack resting on rollers 10 to be moved out from under the clamped stack, to reverse motor 28 to lower the frame 20 and clamped sheets.

As the frame 20 approaches its lowermost position, it strikes limit switch 86, designed to cause clamping plates 62 to move to the retracted position with lingers 66 still extending horizontally, allowing the stack of sheets to fall to and rest again on the conveyor belt 14. Limit switch 86 also acts to reverse motor 2S to again cause the motor to move upwardly.

Limit switch 88 acts soon after the commencement of the upward travel to allow cylinder 74 to rotate ngers 66 to the retracted position soon after the frame is suficiently high above belt 14 to allow such rotation without clashing with the rollers it).

The method by which the limit switches 82-87-84- 36-83 control the operation will now be described. Many types of limit switches could be provided, all within the scope of the invention. Similarly the methods of utilizing such limit switches to control the elements shown are Well known and the functions of the controls operated by the limit switches are described, but it is understood that any one of a number of such controls might be employed.

Limit switch 82 is located to correspond to the desired unit stack height and is near the upper limit of frame travel. Switch 82 operates controls during the upper travel of frame 2t) to supply fluid to energize cylinder 74 to move clamping plates 62 forward.

Limit switch 34 is located to set the upper limit 0f frame 20 and is located sufciently high above limit switch 82 to allow the ngers 66 to move from retracted to extended position clear of the upper sheet of the unit stack. Actuation of limit switch 84 by the upward travel of frame 29 (a) energizes cylinder 74 to rotate fingers 66 up under the lowermost clamped sheet; (b) energizes motor 16 to move belt 14 and thereby to move the unit stack from beneath the frame, and (c) with a suitable time delay reverses the motor 28 to lower the frame.

Limit switch S7 controls the differential height between the top of the stack and the roller 44 as already described.

Limit switch 86 is located to correspond to the lower limit of frame movement where the clamped sheets are low enough to be set on the rollers 10. Actuation of limit switch 86 by the downward movement of frame 20 retracts the clamping plates 62 and fingers 66, the latter still in extended position, and reverses the operation of motor 28 to cause the sequential upward motion of frame 20. The retraction of clamping plates 62 releases the formerly clamped sheets on to rollers 10 to form the base of a further stack.

Limit switch 88 is located above the limit switch 86 connected to cause the fingers 66 to rotate from extended to retracted position without contacting rollers 10. Actuation of limit switch 88 by the upward movement of frame 2i) causes the energization of cylinder 74 to move the fingers from extended to retracted position.

The reason for having greater height between the roller 44 and the top of the stack, at lower stack heights is to ensure that the sheets strike backstop 30 before brushing the top of the stack, and therefore settle vertically onto the stack top. This is done because in many applications of the invention (such as when it is employed in stacking the output of a printer-slotter), ink, not as yet dry, is on the sheets. Such ink will not be smeared when the sheets drop vertically onto the stack, but might well be smeared if brushed horizontally by a sheet. By height control and control of belt 76 smearing may be avoided. However as the stack approaches its full height, the angle of inclination of the sheets, as determined by the angle of belt 76, is such that the sheets tend to carry across to the backstop without the lead edge of the sheet dropping down to smear the printing at the top of the stack, and under these conditions the difference in height between roller 44 and the top of the stack can be decreased. Hence the hydraulic control or cylinder 50 to move rods 51 downwardly is used.

This lowering, where possible, is desirable'since it permits a given stack height to be built up with a lower maximum height of roller 44. Another feature of the height control is that the maximum height of roller 44 above the top of the stack must not be so great as to allow the sheets to tumble before reaching the stack.

During the downward travel of the stack and the frame 20, the cylinders 50 are hydraulically actuated in the opposite direction so that the roller 44 is again raised to its greater height relative to the top of the stack.

The control circuitry will now be described as shown in FIGURES 4, 5 and 6.

Limit switch 86 is arranged, when actuated, to close a normally open line 104 from the positive supply 100 through relay 106 to ground 102. Line 104 on the negative side of switch 103 is also connected through the solenoid of a relay 110 to ground.

Limit switch 88 is arranged, when actuated, to close normally open switch 112 which connects the positive line through the solenoid of relay 116 and through switch 190 to ground.

Limit switch 82 is arranged, when actuated, to close the normally open switch 118 to connect the solenoid 120 between the positive line and ground.

Limit switch 87 is arranged, when actuated, to close normally open switches 122 and 124. Positive line 100 is connected through a normally open switch 126, switch 122 and relay 130 to ground. The positive line 100 is also connected through a switch 128 through normally open switch 124 and relay 132, in series, to ground. Switches 126 and 128 are ganged and arranged so that when one switch is open the other is closed, for a purpose to be hereinafter described.

Limit switch 84, when actuated, closes normally open switch 134 which connects the positive line:

(a) Through relay 136 to ground.

(b) Through switch 139 'and relay 138 to ground, and

(c) Through relay 140 to ground.

Relay 140, when energized, closes normally open switch 142 which connects the positive line through relay 144 to ground. Relay 144 when energized closes normally open switch 146 which connects the positive line through a relay 148 to the negative line. Relay 138, when energized, closes a normally open switch 150 which connects one terminal of a power supply 152 through motor 16 and normally closed switch 154 to the other terminal of the motor power supply 156. Relay 140 when energized opens normally closed switch 154.

The control of motor 28 Power for motor 28 is carried through terminals 158 and 160 for connection to the positive and negative power sources for the motor 28, and motor 28 will usually be a D.C. motor for directional control hence terminal 158 will be positive and 160 will be negative. A switch 162 is operable between two sets of terminals, the upper set marked R, which connect one terminal of motor 28 to 158 and the other terminal to terminal 160 and to the other terminals L which reverse the connections for the motor whereby its rotation will be reversed. The motor connection from positive terminal 158 which is unique to the corresponding terminal R is broken by a normally closed switch operated by the photo cell 80. The position of switch 162 may be caused to move to the raise position by the relay 106, and to move towards the lower position by relay 148.

In operation, therefore, as the downwardly moving frame 20 closes limit switch 86, switch 103 is closed energizing relay 106 to move the switch 162 to the raise position` Assuming that photo cell V80 is now energized because there are no cards between the source 81 and the cell 80, switch 164 will remain open leaving the motor oi until the cards rise to include the photo cell light path. When the cards cut oi the light path, the switch 164 will close and the motor 28 will raise the frame 20 until photo cell 80 is again energized and this intermittent operation will continue until the frame reaches its upper position.

However, it will be noted that switch 162 controls the position of ganged switches 126 and 128 and that when switch 162 moves to the -raise position switch 128 is opened and switch 126 is closed. The closing of switch 126 completes the circuit from the normally open switch 122 to the positive line. Thus when the rising carriage reaches switch 87, switch 122 is closed, energizing relay to be discussed hereafter. Switch 124 is also closed rby the actuation of limit switch 87 but relay 132 is not energized since switch 128 will then be open. As frame 20 continues to rise, when limit switch 84 is closed relay is energized, closing (after the design time delay) switch 142, energizing relay 144, closing switch 146 and energizing relay 148 which moves the switch 162 from the raise to the lower position. This will cause the motor 28 to reverse and lower the frame 20 and this lowering is now independent of the operation of the photo cell. At the same time it will be noted that switch 128 is now closed and switch 126 open so that the descending frame passing limit switch 87 will close the circuit to relay 132 but will not close the -circuit to relay 130. The downward motion of the frame 20 will continue until limit switch 86 is again closed which will lagain reverse the position of switch 162 and cause the motor 28 to raise the carriage subject to the position of switch 164 determined by photo cell 80. Switch 162 is connected to operate switch 139 whereby when switch 162 is in the raise position switch 139 is closed and when switch 162 is in the lowei position switch 139 is open.

Braking means, not shown, will be provided associated with the motor, for preventing the falling of the frame 20 during times or in the event that mot-or 28 is not energized.

Dierential control As seen in FIGURE 5, relays 130 and 132 control the position of a reversing valve 178, which may connect a hydraulic source either to a line 174 or a line 176, depending on which relay is energized, and the arrangement of valve 178 is such that when neither solenoid is energized, the valve assumes a neutral position shutting oii both lines 17 4 and 176 from the source land pump. It will also be seen that whichever line is connected to the source, the other line will be connected to the sump. Line 174 is divided to form two lines 174a and 174b connected (when line 174 is a source line) to raise the two piston rods 51 (see FIGURE 1), while line 176 divides into two lines 176a and 176b active when line 176 is the source to lower the two piston rods 51. The valve 178 may be adjusted so that, when actuated by a relay, it will remain in position long enough to eiect the desired raising or lowering motion or alternatively the limit switch 87 may be so designed and the length of piston stroke under upward or downward operation may be made adjustable to control the diierential raising and lowering and allow adjustment of the amount thereof.

The effect of the apparatus is that when the rising carriage depresses switch 87, switch 126 is closed, energizing relay 130 to conne-ct source 170 to lines 176 to lower the pistons and reduce the spacing between the roller 44 and the top of stack. Relay 132 is not then energized because switch 128 is open. On the other hand, when the carriage is passing downwardly and operates limit switch 87, switch 128 is closed and switch 126 is open, whereby limit switch S7, by closing switch 124, energizes solenoid 132 and by the operation of valve 178 raises the pistons and again increases the spacing between the roller 44 and the topof the stack.

Operation of clamping plates 62 and fingers 66 Relays 110 and 120 are connected to operate control valve 180 located between a pneumatic supply and the cylinder 64 which controls the position of the clamping plate 62. As the frame 20 is rising, limit switch 82 is closed to energize relay 120 which moves a reversible valve 180 to a position to connect a pneumatic supply line 184 connected to a source (not shown) to the rear of cylinder 64, while the front of cylinder 64 is connected by the same valve to exhaust line 186, actuating the piston in cylinder 64, to move the clamping plates 62 forward. Due to the design of switch 180, operated by the relays 120 and 110, the switch remains in this position until the energization is reversed by the other relay 110. Relay 110 is energized during the downward motion of the frame 20 as it passes limit switch 86 and relay 110 thereby reverses the position of switch 180 and by the connection of source line 184 to ythe forward portion of cylinder 64 acts to retract the rod operated by cylinder 64 and hence the clamping plates 62. Valve 180 is connected to operate a switch 190, so that, when valve 180 is in position to move clamping plates 62 to clamping position, switch 190 is open, and when valve 180 is in position to move plates 62 to retracted position, switch 190 is closed.

Operation of fingers 66 The lingers 66 are operated in a similar manner due to a valve 182 which may connect to either line of the cylinder 74, a source line 184 or return line 186. The rising carriage actuates limit switch 88, energizing relay 116 (switch 190 then being closed) to move piston rod 72 in a direction away from the stack, retracting the lingers 66. As in valve 180, the valve 182 remains in this position until switch 84 is closed, energizing relay 136 to reverse the position of valve 182 and thereby to move piston rod 72 toward the stack to rotate fingers 66 forwardly.

Operation The general operation of the device is therefore as follows: Initially frame 20 will be assumed at its lowermost position with clamps 62 retracted and iingers 66 in extended position, although they are clear of the extended or existing stack location. The motor 28 for raising frame 20 is stationary as there should, at this time, be an uninterrupted light path between source 81 and photocell 80 maintaining switch 164 open. Sheets are supplied to belt 76 from a source of such sheets to be stacked, such as a printer-slotter. It will be noted that, assuming a constant supply to belt 76 if belt 76 is operating rapidly, the sheets will be spaced one from another on the belt, but if the belt is run slowly, the sheets will appear on belt 76 in shingle formation. Either way the sheets are fed off the end of belt 76 and move over to the back stop 30, then falling into a stack on rollers 10 under the guidance of back stop 30 and surfaces 56.

When the height of the sheets rises to interruptthe light path to cell 80, allowing switch 164 to close, switch 162 is lthen in the raised position, energizing motor 28 to raise the frame 20. As the motor 28 is adjusted to operate at a predetermined rate faster than the rate of rise of the stack, the motor 28 is then intermittently turned on and off by the control of cell 80 to maintain the frame 20 rising at a rate averaging out to the rate of rise of the stack. When frame 20 reaches limit switch 88, switch 112 is closed thereby, and relay 116 is energized (switch 190 being then closed) to move piston rod 72 to the right and move the lingers 66 to the retracted position. The frame 20 continues -to rise at a rate determined by the raising motor 28 until switch 87 is closed by frame 20, which energizes relay 130 but not relay 132 to connect the source of hydraulic pressure to line 176 to lower rods 51 to reduce the spacing between the roller 44 and the top of the stack.

When the still rising stack reaches the desired height for a unit stack of sheets, limit switch 82 is operated by frame 20 t0 energize relay 120 which moves switch 180 to connect the pneumatic source line 184 to the end of cylinder 64 to advance plates 62 forward to clamp the sheets opposite the plates 62 between them and the back stop 30, whereby such sheets operate to act as a shelf for the still falling sheets still being delivered bybelt 76. At the same time the movement of switch 180 opens switch 190. The frame 20 continues to rise until suflicient clearance exists between frame 20 and the top of the unit stack to allow easy removal of the latter and to allow operation of the fingers 66 to extended position. The frame 20 next operates limit switch 84 which closes switch 134 which actuates relay 138, closing normally open switch 150 and energizing motor 16 to move belt 14 carrying out the -unit stack from the stacking location. Limit switch 84 is designed, or the apparatus may be otherwise designed, to maintain switch 150 closed in suliicient time to remove the u nit stack on rollers 10. At the same time the closure of switch 134 actuates relay 136, which acts to connect pneumatic source line 184 to the rear of cylinder 74 to advance rod 72 toward the stack and to rotate the fingers 66 to the extended position. Thus any sheets imperfectly or partially clamped by clamping plates 62 are straightened and held firmly in position by fingers 66.

At the same time the closure of switch 134 has operated time delay relay 140, which after a suitable time to allow the lingers 66 to operate and the unit stack to be removed, closes switch 142 and energizes relay 144 to operate switch 146 which energizes relay 148 which operates switch 162 to reverse the operation of motor 28 and to cause it to lower frame 20. (It will be noted that the basic requirement for operation of motor 28 is that time delay relay 140 allow sufficient time for removal of the unit stack before switching motor 28 to move frame 20 downwardly. In the preferred embodiment it will be -noted that the switching for motor y28 is such that the frame travels upwardly during this interval. It will be realized, with the proper changes in circuitry, that the circuit may provide that the motor halts after the operation of limit switch 84, for the duration of the time delay interval, before causing frame 20 to travel downward.)

At the same time relay 140 is connected to open normally closed switch 154, halting the operation of motor 16, the time allowed by the delay relay being sutcient to allow removal of the stack. As the downwardly moving frame 20 passes limit switch 84 it will be noted that no further effect will take place as the iingers are already advanced, the motor is already reversed and the motor 16 will not operate a second time since interlock means are provided in the form of switch 139, operable Iby motor switch 162 when in the lower position to open the circuit to relay 138.

As the frame passes limit switch 82 no effect is created on the clamping plates which are already advanced. As the frame continues downwardly, it actuates limit switch 87 and switches 122 and 124 are 4again closed. However, only solenoid 132 is energized, wlt'ch has the effect of reversing the position of switch 178 to connect the source to lines 174 and to again raise the rods 51 to increase the distance between the roller 44 and the top of the stack. As the frame passes limit switch 88 no effect is caused upon the lingers 66 since, although switch 112 is closed, there is provided a switch 190 which is ganged to the position of valve 180 to be open when the clamps 62 are advanced, and thus tin-gers 66 may only `be retracted when the clamps are retracted and therefore only during the upper travel of the frame 20. The frame continues downwardly to lower the frame 20 with the clamped sheets to a position just above the rollers 10. In this position frame 20 operates limit switch 86, energizing relay 106 to reverse the. motor yand energizing relay 110 to retract the clamping plates (closing switch and allowing the formerly clamped sheets to rest on the rollers 10 now allowing the frame 20 to rise under the control of -photocell 80 in the manner already described.

As already described, when the frame 20 has risen suiciently above the rollers 10 for fingers 66 to be retracted, this is accomplished by limit switch 88 since switch 190 is now closed by the position of valve 180 to the right in the drawings. It will `be noted that, in

accordance with the above described oper-ation, a stack of sheets has been formed, removed and a new stack started without the necessity of halting the delivery of sheets "by vbelt 76 from the supply.

The cycle as now described is repeated.

What I claim as my invention is:

1. Means for the continuous stacking of sheets comprising: a frame having mounted thereon, first guide extents extending generally vertically; second guide extents spaced from said first yguide extents, arranged and oriented to guide sheets into position with one edge extending -along said first guide extent and the other edge extending along said second guide extent, whereby sheets may 'be stacked one on the other with the edges in such relationship; clamping surfaces mounted on said frame to move from a. retracted position clear of such stack to an extended position to clamp sheets in said stack between such clamps and said rst guide extents; -base for supporting sheets stacked between said first and second extents, and means for gradually raising said frame relative to said base.

2. Means for the continuous stacking of sheets comprising: la surface; a generally vertical guide extent extending upwardly relative to said surface, designed and constructed to form a guide for one edge of sheets stacked on said surface; means for supplying such sheets, and progressively Iarranging them in a stack on said surface, with one edge of each sheet adjacent said =guide extent; means for progressively raising said guide extent as said stack grows in height; clamping means vertically movable with the `guide extent movable from a retracted position free of the edges of sheets opposed to those adjacent said guide extent, to ran extended position whereat pressure is exerted by said clamping means on certain of said opposed edges to clamp them against said guide extent.

3. Means as claimed in claim 2, including means, actuable when said stack has reached a predetermined height relative to said surface, to actuate said clamping means.

4. Means las claimed in claim 3, including means actuable when said stack has reached a greater predetermined height, to cause removal of the stack supported by said surface and to lower the stack supported -by s-aid edge and clamping means toward said surface.

5. Means as claimed in claim 4, including means actuable on the lowering of `said stack to a predetermined height to move said clamping means to the retracted position.

6. Means as claimed in claim 1, including means actuable after operation of said clamping means from retracted to extended position, to move a supporting surface into position, bearing upwardly on the lowermost clamped sheet.

7. Means as claimed in claim 2, including means actuable after operation of said clamping means from retracted to extended position, to move a supporting surface into position, bearing upwardly on the lowermost clamped sheet.

8. Means for stacking similar sheets aligned with one another on a base surface, with one edge of such sheets adjacent a side surface which is arranged and oriented to extend roughly transversely to said sheets when so stacked; clamping means, designed and constructed to move between a retracted position clear of said stack and an extended position, and in said extended position to exert pressure on edges of stacked sheets opposed to edges of the same sheets adjacent said side surface, whereby such same sheets are clamped between said side surface and said clamping means, said clamping means being normally retracted, means actuable when such stack has reached a predetermined height above said surface for moving saidv clamping means from retracted to extended position.

9. Means as claimed in claim 8, wherein means are provided for raising said side surface and clamping means together during a period where the whole of said stack bears on said surface; means are provided for lowering said side surfaces and clamping means together a predetermined time after said clamping means have moved to the extended position, and means are provided for moving said clamping means to the retracted position when said clamping means and support together have reached a predetermined location adjacent said base surface.

10. A method of stacking sheets, comprising the steps of: continually stacking said sheets in aligned relationship and with the flat sides of such sheets in contact, by continually adding sheets to the top of such stack; when such stack reaches a predetermined height, clamping sheets spaced from the bottom of said stack by opposed edges, and continuing to add sheets to the top of said stack during the period of clamping, the sheets beneath said clamped sheets being removed from said stack during said period of clamping.

11. A method as claimed in claim 10, wherein said clamped sheets and sheets thereabove are not lowered for a predetermined time interval after said clamping step.

12. A method -as claimed in claim 11, wherein said sheets beneath said clamped sheets are removed during said predetermined interval, and thereafter said clamped sheets are lowered to the vicinity of the original location of the bottom of said stack, where said clamping is released.

13. A method of stacking sheets, comprising the steps of: continuously stacking said sheets in aligned relationship and with the flat sides of such sheets in contact, by continually adding sheets to the top of such stack; when such stack reaches a predetermined height, clamping sheets spaced from the bottom of said stack by opposed edges, and continuing to add sheets to the top of said stack during the period of clamping, said clamped sheets and sheets thereabove being raised for a predetermined distance after said clamping step.

References Cited by the Examiner UNITED STATES PATENTS 2,821,391 1/1958 Buccicone 27186 2,960,243 11/ 1960 Beaulieu 271-86 X 3,198,518 8/1965 Carlson 271--86 M. HENSON WOOD, IR., Primary Examiner.

J. N. ERLICH, Assistant Examiner. 

1. MEANS FOR THE CONTINUOUS STACKING OF SHEETS COMPRISING: A FRAME HAVING MOUNTED THEREON, FIRST GUIDE EXTENTS EXTENDING GENERALLY VERTICALLY; SECOND GUIDE EXTENTS SPACED FROM SAID FIRST GUIDE EXTENTS, ARRANGED AND ORIENTED TO GUIDE SHEETS INTO POSITION WITH ONE EDGE EXTENDING ALONG SAID FIRST GUIDE EXTENT AND THE OTHER EDGE EXTENDING ALONG SAID SECOND GUIDE EXTENT, WHEREBY SHEETS MAY BE STACKED ONE ON THE OTHER WITH THE EDGES IN SUCH RELATIONSHIP; CLAMPING SURFACES MOUNTED ON SAID FRAME TO MOVE FROM A RETRACTED POSITION CLEAR OF SUCH STACK TO AN EXTENDED POSITION TO CLAMP SHEETS IN SAID STACK BETWEEN SUCH CLAMPS AND SAID FIRST GUIDE EXTENTS; BASE FOR SUPPORTING SHEETS STACKED BETWEEN SAID FIRST AND SECOND EXTENTS, AND MEANS FOR GRADUALLY RAISING SAID FRAME RELATIVE TO SAID BASE. 